This is a Design I made in 2022 bcs then I finally had the chance to acquire a THS720A for a reasonable Price but with NO external Charger,

therefore I designed my own rather searching to find one that is not cheap. A friend of mine made me a 3D Printed case Design using my Specifications. The 3D Design and Files will be in another Shared Project.

The Charger can be Powered either from a Wall-Wart 5V or the 12V Power Supply, the default is the 5V PSU with ca. 2Amps. If a 12V one is to be used, a onboard DCDC (Mini360) Buck must be populated along with 2 Caps (C1,C4). Further ans Onboard DC Barrel Connector or a Optional a 2 Pin Screw Terminal can be used

These Mechanical Parts from Aliexpress are Needed along with some Metal Standoffs (Pictures are in the Mechanics.zip File):

https://www.aliexpress.us/item/32953210416.html?spm=a2g0o.order_list.order_list_main.10.273a18029lb5BO&gatewayAdapt=4itemAdapt

https://www.aliexpress.us/item/2251832763539664.html?spm=a2g0o.order_list.order_list_main.15.273a1802TbbJIL&gatewayAdapt=glo2usa4itemAdapt

More Info's & Pictures see my Post on the EEVBLOG: https://www.eevblog.com/forum/testgear/tektronix-ths710-ths720-ths730-external-battery-charger-build/msg4840787/#msg4840787

I used a Standalone StepUp Charger Chip (Asian Brand) that offers all the Features I wanted, the only drawback of this Chip is the limited Status Signaling, just Charging or Charged.

This problem I solved with an additional ATTINY85 that takes care of the Signaling using a WS2812B type Intelligent LED.

Following the LED Statuses :

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Green Blinking : Battery not detected or not Inserted

Blue Steady : Charging

Green Steady : Charged

Red Steady : Output or Battery shorted or Battery too low inner Resistance

Please check my YouTube videos on this design and many more at https://www.youtube.com/@KonstantinGrigoriadis